Process for forming a membrane filtration apparatus

ABSTRACT

A filtration apparatus is provided which is formed from multilayer presealed elements and monolayer elements that are insert molded together. The device is provided with a feed port, a filtrate port and, optionally, a retentate port. The sealing configuration of the presealed elements and the seal provided by the insert molding step effect a seal configuration that causes a feed liquid to be filtered to form a filtrate such that the filtrate is not mixed with either the feed or a retentate.

This application is a divisional of application Ser. No. 08/840,529filed Apr. 22, 1997, now U.S. Pat. No. 5,922,200, which is a divisionalof 08/624,830 filed Mar. 27, 1996, now U.S. Pat. No. 5,824,217.

BACKGROUND OF THE INVENTION

This invention relates to a membrane filtration apparatus for effectingfiltration of a liquid composition wherein a feed liquid is introducedinto the apparatus and,a filtrate stream is removed from the apparatus.More particularly, this invention relates to a tangential flow membranefiltration apparatus or dead ended membrane filtration apparatus whichare formed and selectively sealed by injection molding of a polymericcomposition.

Prior to the present invention, liquids have been filtered within aplurality of filter modules that are stacked between manifolds orindividually sealed to a manifold plate. Each module includes a one ormore filter layers separated by appropriate spacer layers, such asscreens, to permit liquid feed flow into the apparatus as well asfiltrate flow from the apparatus. Filtration within the module can beconducted as a tangential flow process wherein incoming feed liquid isflowed tangentially over a membrane surface to form a retentate and afiltrate. Alternatively, filtration can be conducted as a dead end modewherein all incoming feed liquid is passed through a membrane filterwith retention of solids and other debris on the membrane filter. Inthis latter mode only a filtrate is recovered.

At the present time, filtrate is sealed from feed within a membranefiltration apparatus by sealing techniques utilizing potting adhesives,solvent bonding or heat sealing. In the case of a tangential flowfiltration apparatus, filtrate is sealed from feed and retentate.Adhesives are undesirable since they have limited chemicalcompatibility, are a source of significant extractable species,introduce process control difficulties, impose bond strengthlimitations, impose use temperature limitations and increase processcycle time. Heat sealing is undesirable since its use imposes alimitation upon the thickness of the material being heat sealed. Inaddition, heat sealing is undesirable because it requires multiplesteps, imposes material compatibility limitations and requires asubstrate to effect heat sealing of filtration elements. Solvent bondingis undesirable since solvents impose environmental limitations andimpose limitations on liquids to be filtered.

Accordingly, it would be desirable to provide a multilayer filtrationapparatus which utilizes a plurality of filtration modules wherein thelayers are appropriately sealed without the use of adhesive, solventbonding or heat sealing. In addition, it would be desirable to provide atangential flow or a dead ended filtration apparatus containing aplurality of filtration modules which can be formed into a stack andwhich can be appropriately sealed to define liquid flow paths within thestack in a one step sealing process.

SUMMARY OF THE INVENTION

In accordance with this invention, a dead ended or tangential flowfiltration apparatus is provided which includes a plurality ofspaced-apart membranes and a plurality of spacer layers having channelsor openings that promote liquid flow therethrough. The dead endedfiltration apparatus are provided with at least one feed port and atleast one filtrate port. The tangential flow filtration apparatus areprovided with at least one feed port, at least one filtrate port and atlease one retentate port. The membranes are included within modules eachof which has at least one membrane layer and at least one spacer layer.The modules are presealed by any convenient means so that they can besubsequently sealed with additional modules and spacer layers by aninsert molding process to form a membrane filtration apparatus formedfrom a stack of membranes and spacer layers which permits filtration ofa liquid. An optional end cap can be provided at each end of the stackto assure liquid flow from the feed inlet to the retentate outlet,through a membrane, and to the at least one filtrate outlet. The spacerlayers are appropriately sealed and side surfaces and end surfaces ofthe membrane filtration apparatus are appropriately sealed by insertmolding with a molten polymeric composition which is caused to migrateinto selected volumes of the spacer layers to effect sealing and toassure liquid flow within the stack, during use, from the feed inlet tothe at least one filtrate outlet. In the case of a tangential flowfiltration apparatus, liquid flow within the stack is assured by sealingthe feed inlet and the retentate outlet from the filtrate outlet. Insertmolding is accomplished by positioning the stack within an injectionmold and injecting the molten polymeric composition into the mold toeffect sealing in a manner that assures the desired liquid flow withinthe final membrane filtration apparatus during use. The spacer layerswhich accept filtrate are sealed by the plastic composition from a feedport extending into the stack so that the feed must pass through amembrane layer prior to entering a filtrate spacer layer. In addition,the spacer layers adjacent to the feed port which are designated toaccept feed remain in liquid communication with the feed channel.Channels which accept either retentate or filtrate also extend into thestack. The channels which accept retentate are sealed from the filtratespacer layers and are in fluid communication with the spacer layerswhich are also in fluid communication with the feed port. The port orports which accept filtrate are sealed from the spacer layers whichaccept feed or retentate and are in fluid communication with the spacerlayers that accept filtrate. The stack is also sealed in a manner sothat liquid feed entering the feed spacer layers must pass through amembrane before entering a filtrate spacer layer. Prior to insertmolding the stack, the stack is formed from single spacer layer unitsand multilayer modules which modules are partially presealed so that, incombination with the final insert molding step, the presealing assuresthe desired liquid flow through the final membrane filtration apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 1A illustrate the process for making one embodiment of atangential flow filtration apparatus of this invention.

FIG. 2 illustrates the process for making a second embodiment oftangential flow filtration apparatus of this invention.

FIG. 3 illustrates the process for making a third embodiment of atangential flow filtration apparatus of this invention.

FIG. 4 is a partial cross sectional view of one embodiment of atangential flow filtration apparatus of this invention.

FIGS. 5 illustrates a process for making an alternative embodiment of atangential flow filtration apparatus of this invention.

FIG. 6 is a partial cross-sectional view taken along line 6—6 of FIG. 5of an embodiment of this invention which can be produced by the processillustrated in FIG. 5.

FIG. 7 illustrates a process for making a dead end flow filtrationapparatus of this invention.

FIGS. 8-23 show labeled single layer and module configurations useful inthe present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The membrane filtration apparatus of this invention is formed from astack of multilayer and monolayer elements including working layerscomprising membranes and spacer layers that provide a flow path for aliquid stream which is directed through the membranes as well asrecovered retentate liquid streams which cannot pass through themembrane. The multilayer elements referred to herein as modules areformed from two or three components, at least one of which is a membranelayer and at least one of which is a spacer layer. The three componentmodule is formed from two membrane layers, each positioned on onesurface of a spacer layer. The monolayer comprises a spacer layer andcan comprise a defined open volume or a porous single layer such as ascreen. When utilizing an open volume as the spacer layer, it is formedwith one or two mating rims forming the perimeter of the open volumewhich separates modules or separates a module and an end of thefiltration apparatus. The modules can be formed from more than threelayers, if desired. The spacer layer comprises an element having holes,channels or an open volume through which liquid can pass. The spacerlayer is contiguous to or contacts a membrane through which liquidpasses.

Modules forming a portion of the stack are presealed prior to beingpositioned within the stack and thereafter insert molded. The presealedconfiguration of the module will depend upon the position of the elementwithin the stack and upon whether the filtration apparatus is tofunction in a tangential flow mode or in a dead end flow mode. Themodule can include either a feed spacer layer or a filtrate spacerlayer. When the module includes the feed spacer layer, the module ispresealed so that the feed spacer layer is open to the feed port and theretentate port in the filtration apparatus and is closed to the filtrateport or ports. When the module includes the filtrate spacer layer, themodule is presealed so that the filtrate spacer layer is closed to thefeed port and the retentate port, and is open to the filtrate port orports. The monolayer elements within the stack forming the filtrationapparatus comprise spacer layers. The membranes utilized in the stackcan comprise ultrafiltration membranes, microporous membranes,nanofiltration membranes or reverse osmosis membranes. In a tangentialflow filtration apparatus of this invention, the feed, retentate andfiltrate ports are arranged so that incoming liquid feed to thefiltration apparatus enters at least one feed channel, passes throughthe feed spacer layers and either passes through a membrane to form afiltrate stream or is retained by a membrane to form a retentate stream.The retentate stream is removed from the filtration apparatus throughone or more retentate ports and the filtrate stream is removed from thefiltration apparatus from one or more filtrate ports. If desired,multiple filtrate ports can be arranged to effect tangential fow on thefiltrate side of the membranes. There is an inlet filtrate port(s) andan outlet filtrate port(s). In tis case a portion of the filtrate can berecycled to the inlet filtrate port or ports as a means for controllingpressure on surfaces of the membranes within the stack. In a dead endflow filtration apparatus of this invention, the feed and filtrate portsare sealed from each other and only filtrate is recovered from themodule. In the final step for forming the filtration apparatus of thisinvention, the stack of at least one module and at least one spacerlayer is positioned within a mold and a flowable, e.g. liquid, polymericcomposition is injected into the mold to seal the stacked elementstogether and to selectively migrate into either the feed spacer layersor the filtrate spacer layers to selectively seal the spacer layersthereby to assure liquid flow through the filtration apparatus describedabove.

Representative suitable membrane filters are ultrafiltration,microporous, nanofiltration or reverse osmosis filters formed frompolyvinylidene fluoride (PVDF), polysulfone, polyethersulfone,regenerated cellulose, polyamide, polypropylene, polyethylene,polytetrafluoroethylene, cellulose acetate, polyacrylonitrile, vinylcopolymer, cellulose acetate, polyacrylonitrile, vinyl copolymer,polycarbonate, PFA, blends thereof or the like. Suitable polymericsealing compositions are those which provide the desired sealingconfiguration within the filtration apparatus and do not signifigantlydegrade the elements forming the apparatus including the membranes,spacer layer ports and housing elements. In addition, the sealingcomposition should not degrade or provide a significant source ofextractables during use of the apparatus. Representative suitablesealing compositions are thermoplastic polymer compositions includingthose based on polypropylene, polyethylene, PFA, PVDF, polysulfones,polyethersulfone, polycarbonate, acrylonitrile-butadiene-styrene (ABS),polyester, blends thereof, filled or unfilled or the like.

Referring to FIGS. 1 and 1A, a filtration apparatus of this invention,10 is formed from a plurality of modules 12 and a plurality of spacerlayers 14. The modules 12 are formed from a feed spacer layer 16 whichcan comprise a screen or the like and two membrane layers 18 and 20 andinclude filtrate ports 1 and 3, feed port 5 and retentate port 7. Themodule 12 is formed by placing the membrane layers 18 and 20 and spacerlayer 16 in a mold and molding a plastic composition around the layersand selectively into the layers to form a first seal about the layersand to form a peripheral raised rib 9. The module 12 is presealed in amanner which will be more fully described with reference to FIG. 4. Themodules 12 a and 12 b as well as the filtrate screens 14 are positionedbetween end caps 22 and 24 within a mold and all of these elements arejoined together to form a second seal by being insert molded within themold. The end cap 22 is provided with filtrate ports 26 and 28, feedport 30 and retentate port 32. The module 10 is shown in FIGS. 1 and 1Ais a tangential flow filtration module since it includes a retentateport 32 from which retentate is collected. A dead end filtration moduleis formed in the same manner but eliminating retentate ports 17 and 32.

Referring to FIG. 2, the membrane filtration apparatus 40 is formed fromtwo modules 42 and 44, and a feed spacer layer 46. In addition, themembrane filtration apparatus 40 can optionally include anti-deflectionend caps 48 and 50 having ribbed interior surfaces 52. The filtrationmodule 40 is formed by insert molding Modules 42 and 44 include twofiltrate outlet ports 54 and 56, a feed inlet port 58 and a retentateoutlet port 60. The anti-deflection caps 48 and 50 include holes 62through which extend the filtrate ports 54 and 56, the retentate outletport 60 and the feed inlet 58 for the modules 42 and 44 respectively.The modules 42 and 44 each are formed from an end cap 43, filtratescreen 45 and a membrane 47. In a first step, the end caps 43, filtratescreen 45 and membrane 47 are placed into a mold and are presealed toform a first overmolded element 35. The overmolded element 35 then isplaced in a second mold and a plastic composition is molded aboutovermold 35 to form second overmolded element 37, including retentateoutlet port 60 and fed inlet port 58. The feed spacer 46 is formed bymolding a rib 39 about a screen having holes 41.

Referring to FIG. 3, an alternative membrane filtration apparatus ofthis invention 49 utilizing a single filtrate exit port 51 on eachmodule is illustrated. The membrane filtration apparatus 49 is formedfrom two modules 53 and 55. The modules 53 and 55 are formed from apremolded cap 57, a filtrate screen 59 and a membrane 61 which aremolded together to form a first overmolded 29. A second overmoldedelement 63 is molded using the first overmolded element 29 to form afeed port 65 and a retentate port 67 and to preseal the modules 53 and55. A feed spacer layer 69 is positioned between the modules 53 and 55.Anti-deflection caps 71 and 73 having ribbed interior surfaces 75optionally can be utilized. The anti-deflection caps 71 and 73 each areprovided with holes 77 which accommodate the ports 65, 51 and 67. Thefiltration apparatus 49 is formed by insert molding.

Referring to FIG. 4, the sealing arrangement for a multilayer embodimentof the membrane filtration apparatus 10 of FIGS. 1 and 1A isillustrated. Prior to being stacked, the module formed of multilayerelements comprising the two membranes 18 and 20 and the feed spacer 16is presealed in the area adjacent to feed port 30 by seal 13 which sealsthe membranes 18 and 20 and the spacer 16 together while leaving spacer16 in open fluid communication with the feed port 30. The modules arepresealed differently at the area adjacent the filtrate ports 26 (FIG.1A) and 28 as compared to the areas adjacent the feed port 30 and theretentate port 32 (FIG. 1A). As shown in FIG. 4, the module is sealed inareas 15 to permit liquid communication between the filtrate layers 14with the filtrate channels 26 or 28. The area adjacent the retentateport 32 (FIG. 1A) is sealed in the same manner as the area adjacent thefeed port shown in FIG. 4. By presealing the modules in this manner,they can be stacked and insert molded to form the filtration apparatusof this invention. The stack of elements, in the final insert moldingstep are positioned between two end caps 17 and 19 which seal the topand bottom of the stack. Thereafter, a molten polymeric composition isinjected into the mold containing the stack to seal the sides of thestack in area 21 adjacent the feed port 30 and to prevent leakage frommodule 10. The molten polymeric composition also seals the feed spacerlayers 16 from fluid communication with the filtrate ports 26 and 28 inareas 25 and to prevent leakage from module 10. The insert molding stepis conducted so as to avoid closing the filtrate spacer layers 14 fromfluid communication with the filtrate ports 26 and 28. Thus, the moldingpolymeric composition 25 does not extend a significant distance into thefiltrate spacers 14 to maintain this desired open fluid communicationwith the filtrate ports 26 and 28. By operating in this manner, a stackof filtration elements can be assembled and selectively sealed in a onestep insert molding process.

Referring to FIG. 5, the membrane filtration apparatus 60 is formed froma stack 62 of monolayer feed spacer layers 64, labeled specifically as64 a, 64 b, 64 c and 64 d, and modules 66 which stack has been insertmolded to form the overmold 68. The overmold 68 seals the side, top andbottom surfaces of filtration apparatus 60. The overmold 68, formed byinsert molding, also seals the internal surfaces of the stack 62 toeffect the desired liquid flow within the stack described above isdescribed below with reference to FIG. 6.

The module 66 is formed from an unbonded laminate 59 which is formedfrom two filter (membrane) layers 61 and 63, filtrate spacer, e.g.screen 65. The molded rim 57 extends about the periphery of the module66 and serves to accommodate feed spacer layers 64 with a molded rim 64e on both of its surfaces. Each filter layer 61 and 63 and filtratespacer layer 65 is provided with two filtrate ports 67 and 69 which arepositioned diagonally to each other and are positioned within tabsections 71, 73, 75, 77, 79 and 81. The tab sections are positioned oneach of these layers. The tab sections 71, 73, 75, 77, 79 and 81 extendaway from central portions of each of these layers so that the portslocated therein can be easily accessed. The feed spacer layers 64 a, 64b, 64 c and 64 d are also provided with tab sections 70 and 72positioned on opposing surfaces 74 and 76 of each spacer layer. Anopening 78 on one of the tab sections 70 forms part of a feed portwithin the apparatus 60 while the opening 80 on the other tab 72 formspart of a retentate port within the apparatus 60. The spacer layers 64a, 64 c, 64 b and 64 d can function as either feed spacer layers or asfiltrate spacer layers by reversing the feed and filtrate ports. Ifspacer payers 64 are filtrate spacer layers, then spacer layer 65becomes a feed spacer. A significant advantage derived from thisembodiment is due to the spaced apart filtrate tab sections 83 and 85formed respectively from tab sections 73, 75 and 71 or 79, 77 and 81. Byalternating their positions, more precise control of molten sealingpolymeric composition flow can be attained. That is, the filtrationelement 60 can be more easily selectively sealed since flow of moltenpolymer composition in the area of each tab section and, therefore eachfiltrate port can be more easily controlled while minimizing anundesirable sealing configuration within the feed port or retentate portformed by opening 78 or the retentate port formed by openings 80.

Referring to FIG. 6, the sealing arrangement for the membrane filtrationapparatus 60 of FIG. 5 is shown. The module 66 (FIG. 5) formed ofmembranes 61 and 63 and filtrate spacer 65 are presealed so thatfiltrate ports 69 a and 67 a are in fluid communication with thefiltrate spacers 65 but not in fluid communication with retentate port80 or feed port 78 (FIG. 5). The final overmold 68 preserves thissealing arrangement and prevents leakage from module 60.

Referring to FIG. 7, a dead end flow filtration apparatus 87 includes afeed port 89 and a filtrate port 91. The filtration apparatus 87 isformed form two multilayer modules 93 and 95, each of which is formedwith the feed port 89 and the filtrate port 91; a spacer layer 97; andtwo antideflection caps 99 and 101 each are provided with a feed portclearance hole 103 and a filtrate port clearance hole 105. Themultilayer modules 93 and 95 can be formed in two steps. In a firststep, a premolded end cap 107, a filtrate screen 109 and a membrane 111are sealed together to form a first overmolded element 113. In a secondstep, the first overmolded element 113 is overmolded to form multilayermodules 93 and 95 with feed ports 89. The filtration apparatus 87 isformed by sealing together end caps 99 and 101, spacer layer 97 andmodules 93 and 95 by an insert molding step which forms outside seal 115and seals filtrate port 91 from feed port 89 and to allow feed to passthrough the membrane 109 to form filtrate.

In FIGS. 8-23, the term, “permeate” is used interchangeably with theterm, “filtrate”. Also, the term, “screen” is used interchangeably withthe term. “spacer layer” n is an integer equal to or greater than one.

Referring to FIG. 8, an embodiment is shown having n permeate screensand n plus 1 modules consisting of a feed screen and a membrane.Filtration can also be effected with only 1 permeate screen and 1 moduleconsisting of a feed screen and a membrane.

Referring to FIG. 9, an embodiment is shown having n feed screens and nplus 1 modules consisting of a permeate screen and a membrane.Filtration can also be effected with only 1 feed screen and 1 moduleconsisting of permeate screen and membrane.

Referring to FIG. 10, an embodiment is shown having 2 end caps, npermeate screens and n plus 1 modules consisting of a feed screen and amembrane.

Referring to FIG. 11, an embodiment is shown having 2 end caps, n feedscreens and n plus 1 modules consisting of a permeate screen and amembrane.

Referring to FIG. 12, an embodiment is shown having 1 permeate screenand 2 modules consisting of a feed screen, a membrane and an end cap.

Referring to FIG. 13, an embodiment is shown having 1 feed screen and 2modules consisting of a permeate screen, a membrane and an end cap.

Referring to FIG. 14, an embodiment is shown having n modules consistingof a permeate screen and two membranes and n plus 1 feed screens.

Referring to FIG. 15, an embodiment is shown having n modules consistingof a feed screen and two membranes and n plus 1 permeate screens.

Referring to FIG. 16, an embodiment is shown having 2 end caps, nmodules consisting of a permeate screen and two membranes and n plus 1feed screens.

Referring to FIG. 17, an embodiment is shown having n modules consistingof a permeate screen and two membranes, n plus 1 feed screens and 2 endcaps.

Referring to FIG. 18, an embodiment is shown having n permeate screensand n minus 1 modules consisting of a feed screen, two membranes and twomodules consisting of a feed screen and a membrane.

Referring to FIG. 19, an embodiment is shown having n feed screens, nminus 1 modules consisting of a permeate screen and two membranes andtwo end modules consisting of a permeate screen and a membrane.

Referring to FIG. 20, an embodiment is shown having 2 end caps, npermeate screens and n minus 1 modules consisting of a feed screen andtwo membranes and two end modules consisting of a feed screen and amembrane.

Referring to FIG. 21, an embodiment is shown having 2 end caps, n feedscreens, n minus 1 modules consisting of a permeate screen and twomembranes and two end modules consisting of a permeate screen and amembrane.

Referring to FIG. 22, an embodiment is shown having 2 end modulesconsisting of an end cap, a feed screen and a membrane, n permeatescreens and n minus 1 modules consisting of a feed screen and twomembranes.

Referring to FIG. 23, an embodiment is shown having 2 end modulesconsisting of an end cap, a permeate screen and a membrane, n feedscreens and n minus 1 modules consisting of a permeate screen and twomembranes.

The following examples illustrate the present invention and are notintended to limit the same.

EXAMPLE I

This example illustrates a method for preparing a tangential flowfiltration apparatus of this invention utilizing insert molding toeffect final sealing within a stack of filtration modules provided withend caps and monolayer spacer layers.

End Cap

The end caps are molded from polypropylene homopolymer. They are moldedin an aluminum mold using a injection molding machine. The mold ispreheated to 130 F and clamped at 10,000 pounds of force. Thepolypropylene homopolymer, at 500 F, is injected with a pressure of 3000psi. The resultant end cap has two female Luer port connections.

First Overmold

In preparation for the next molding step a piece of polypropylenepermeate screen and a piece of Millipore Biomax® 10 (polyethersulfone onnonwoven polypropylene), available from Millipore Corporation, Bedford,Mass. are die cut using a steel rule die. The permeate screen, a twillweave, has a thickness of 0.012 inch and has a strand count of 71×71strands/inch.

The end cap, permeate screen and piece of Biomax® 10 membrane are placedtogether in an aluminum mold to create the first subassembly referred toas the First Overmold. The mold is aluminum and incorporates a slidinginsert which exerts a clamping force on the assembly while molding. Themold is preheated to 130 F and clamped at 10,000 pound of force. Theinsert is clamped at 1500 pounds of force. The polypropylenehomopolymer, at 500 F, is injected with a pressure of 3000 psi. Theresultant structure is the First Overmold subassembly.

Second Overmold

In this step the First Overmold subassembly is modified by the additionof feed and retentate Luer ports and by adding a bonding surface aroundthe perimeter of the membrane. This is done by placing the firstovermold subassembly in an aluminum mold with a sliding insert. The moldis preheated to 130 F and clamped at 10,000 pounds of force. The insertis clamped at 1500 pounds of force. The polypropylene homopolymer at 500F, is injected with a pressure of 3000 psi.

The resultant structure is the Second Overmold subassembly. This secondovermold process is then repeated for another subassembly.

Feed Spacer

The feed spacer is woven polypropylene screen to which a solidpolypropylene perimeter is added. The twill woven screen has a thicknessof 0.016 inch and features a strand count of 51×51 threads/inch.

A steel rule die is used to cut the perimeter of the screen and two0.156 inch diameter alignment holes in either end of the screen. Thespacer is created using an aluminum mold with a sliding insert. The moldis preheated to 130 F and clamped at 10,000 pounds of force. The insertis clamped at 1500 pounds of force. The polypropylene homopolymerpolymer, at 500 F, is injected with a pressure of 3000 psi to form theFeed Spacer.

Deflection Cap

The polymer used for the deflection caps is a 30% glass filledpolypropylene. The caps are molded in an aluminum mold and preheated to130 F and clamped at 10,000 pounds of force and injected with pressureof 4,500 psi.

Final Overmold

A feed spacer is sandwiched between two of the second overmoldassemblies together with two deflection caps. The final unit is createdby overmolding this assembly using molten polypropylene homopolymer toencapsulate/bond the perimeter. This is accomplished in an aluminum moldwith a sliding insert. The mold is preheated to 130 F and clamped at10,000 pounds of force. The insert clamps the assembly at 1500 pounds offorce. The polypropylene homopolymer, at 500 F, is injected with apressure of 3000 psi.

Finished Unit

The finished unit has 19 cm² of Biomax® 10 membrane area. Hydraulictesting of this module gave the following results:

Wetted Air Integrity 0 SCCM @ 30 psi Feed Channel Pressure Drop 10 psi @50 ml/min Q_(f) Water Permeability 19 LMH/psi 6% BSA, 8 C flux 127 LMH @Q feed, 38 cc/min. + TMP, 45 psi

What is claimed is:
 1. The process for forming a membrane filterapparatus of unitary seated construction for carrying out tangentialflow filtration which comprises: positioning within an injection mold astack of (a) at least one module layer including at least one membranefilter and at least one first spacer layer and (b) at least one secondspacer layer positioned adjacent each said at least one module layered;said stack having at least one feed port, at least one retentate portand at least one filtrate port, said at least one feed port and said atleast one retentate port being in fluid communication with each other,each of said at least one filtrate port being sealed from fluidcommunication with both said at least one feed port and said at leastone retentate port; said at least one module layer being sealed to forma perimeter seal about said at least one first spacer layer, and said atleast one membrane filter and to form a first port seal which isolatessaid at least one filtrate port from said at least one feed port andsaid at least one retentate port, and injecting a molten polymericcomposition into the said mold having the stack therein to provide aperimeter seal about the periphery of said at least one second spacerlayer and said at least one module layer which seals said at least onefeed port and said at least one retentate port from said at least onefiltrate port and which permits fluid flow within the apparatus tointroduce a feed into the apparatus and to remove a retentate and afiltrate from the apparatus.
 2. The process of claim 1 wherein said atleast one module layer has two sets of filtrate tab sections having aport for a filtrate port, said filtrate tab sections being positioned onopposing surfaces of each of said at least one module layer so that saidfiltrate tab sections on a first of said at least one module layer arespaced apart from filtrate tab sections on each of said at least onemodule layer adjacent said first of said at least one module layer. 3.The process of claim 1 wherein said at least one module layer has twosets of feed tab sections having a port for a feed port, said feed tabsections being positioned on opposing surfaces of each of said at leastone module layer so that said feed tab sections on a first of said atleast one module layer are spaced apart from feed tab sections on eachof said at least one module layer adjacent said at least one firstmodule layer.
 4. The process for forming a membrane filter apparatus ofunitary sealed construction for carrying out dead end flow filtrationwhich comprises: positioning within an injection mold a stack of (a) atleast one module layer including at least two membrane filters and atleast one first spacer layer and (b) at least one second spacer layerpositioned adjacent each said at least one module layer, said stackhaving at least one feed port, and at least one filtrate port, each saidat least one filtrate port being sealed from fluid commutation with saidat least one feed port said at least one module layer being sealed toform a perimeter seal about said at least one first spacer layer andsaid at least two membrane filters to form a first port seal, at one ofat least two parts, which isolates said at least one filtrate port fromsaid at least one feed port, and injecting a molten polymericcomposition into said mold to provide a perimeter seal about theperiphery of said at least one second spacer layer and said at least onemodule layer which seals said at least one filter port and which permitsfluid flow within the apparatus to introduce a feed into the apparatusand to remove a filtrate from the apparatus.
 5. The process of claim 4wherein said at least one module layer has two sets of filtrate tabsections having a port for a filtrate port, said filtrate tab sectionsbeing positioned on opposing surfaces of each of said at least onemodule layer so that said filtrate tab sections on a first of said atleast one module layer are spaced apart from filtrate tab sections oneach of said at least one module layer adjacent said first of said atleast one first module layer.
 6. The process of claim 4 wherein said atleast one module layer has two sets of feed tab sections having a portfor a feed port, said feed tab sections being positioned on opposingsurfaces of each of said at least one module layer so that said feed tabsections on a first of said at least one module layers are spaced apartfrom feed tab sections on each of said at least one module layeradjacent said at least one first module layer.